I have not made any lithium batteries. As we know, graphite is the superposition of graphene layers, and is anisotropic. Is the diffusion direction of lithium ion (from the anode to the cathode or inverse) vertical or parallel to the graphene layers? What effects does the anisotropy of graphite have on the properties of lithium ion batteries?
Very minimal effect as the transport is primarily through the plane of the electrode (as the electrodes are very thin compared to the lateral direction). However, this might not be true if we go to thick electrodes or 3D architectures where transport in other direction will play a role.
Very minimal effect as the transport is primarily through the plane of the electrode (as the electrodes are very thin compared to the lateral direction). However, this might not be true if we go to thick electrodes or 3D architectures where transport in other direction will play a role.
Xiadong,
See the following (recent paper):
S. Shi, P. Lu, Z. Liu, Y. Qi, Yue, L.G. Hector, Jr., S. Harris, ”Direct Calculation of Li-ion Transport in the Solid Electrolyte Interphase,” J. Amer. Chem. Soc. 134 (2012) 15476-15487.
The active site is the only edge plane. There are no paths from the basal plane. However, the defects on the basal plane can be the active sites. The detail is described in my paper.
in addition to the nice work by the Harris group, there is also a nice paper by the ceder group on the solid state diffusion in graphite:
Lithium Diffusion in Graphitic Carbon
http://pubs.acs.org/doi/abs/10.1021/jz100188d
and you may also find our recent paper on the influence of electrode microstructure on battery performance interesting. the key word is tortuosity anisotropy which is especially important for most graphite particles since they tend to have high aspect-ratios:
Tortuosity Anisotropy in Lithium-Ion Battery Electrodes
http://onlinelibrary.wiley.com/doi/10.1002/aenm.201301278/full
best, martin
Thank you very much！You offer a lot of information.They are very useful to me！
Hi, Ebner, may I ask you for the fulltext of 'Tortuosity Anisotropy in Lithium-Ion Battery Electrodes'. I can not download the paper.
Hi, Zhu, you can download it from our website http://lne.ee.ethz.ch/uploads/tx_ethpublications/TortuosityAnisotropy2013.pdf
best, martin
Ebner, thank you very much!
I make clear that Li diffusion is always parallel to the graphite planes. There are no paths from the basal plane as Takeshi Abe said. But the orientation of graphite particle also will affect the batteries properties. Thanks for your recommendation, and I will read carefully.
Takeshi is right. Engineered graphite particles with tailored PSDs and particle shape are used for commercial electrodes. What matters most is efficiency, capacity and rate capability which can be influenced by film density, crystallinity of the graphite, PSD, BET, etc..
Cheers
Ruediger
Hi, Schweiss, are graphite particles monocrystal or multicrystal in industry? Are there many defects in graphite?
You can find some details in the technical papers from Timcal, a famous supplier of graphite, I should say of graphites (with an s !). Among them, a rather spherical one aimed at being used in Li batteries.
See :
http://www.timcal.com/Scopi/Group/Timcal/timcal.nsf/pagesref/MCOA-7S6H6L/$File/High_purity_graphite_powders_for_high_performance.pdf
and especially :
http://www.timcal.com/scopi/group/timcal/timcal.nsf/pagesref/MCOA-7S6K2K/$File/Brochure_Carbon_Powders_for_Lithium_Battery_Systems.pdf
Alain
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